The origin of grand minima in the sunspot cycle

TL;DR

This paper investigates the origins of grand minima in the sunspot cycle by using a flux transport dynamo model to estimate how often such minima occur due to fluctuations in solar magnetic field generation.

Contribution

It introduces a theoretical approach to quantify the frequency of grand minima using a flux transport dynamo model with Gaussian fluctuations based on recent solar cycle data.

Findings

Approximately 1-4% of sunspot cycles may lead to grand minima.

The model aligns with historical data indicating about 2.7% of cycles experienced grand minima.

Fluctuations in poloidal field and meridional circulation are key factors.

Abstract

One of the most striking aspects of the 11-year sunspot cycle is that there have been times in the past when some cycles went missing, a most well-known example of this being the Maunder minimum during 1645-1715. Analyses of cosmogenic isotopes (C14 and Be10) indicated that there were about 27 grand minima in the last 11,000 yr, implying that about 2.7% of the solar cycles had conditions appropriate for forcing the Sun into grand minima. We address the question how grand minima are produced and specifically calculate the frequency of occurrence of grand minima from a theoretical dynamo model. We assume that fluctuations in the poloidal field generation mechanism and the meridional circulation produce irregularities of sunspot cycles. Taking these fluctuations to be Gaussian and estimating the values of important parameters from the data of last 28 solar cycles, we show from our flux transport dynamo model that about 1-4% of the sunspot cycles may have conditions suitable for inducing grand minima.